Read What's wrong with the Mountain Lion interface. Note, especially, the following:

In Mountain Lion’s default setup, I have to scroll-drag in every single window to see if there’s additional content. You can set them to be permanently visible in System Preferences, which I always do, but they’re invisible by default. A user new to the platform, though, would have to discover this fact on their own—and it’s not obvious where to go to change the setting.

Since I don't have ML, I can't tell you exactly which preference pane has the ability to change this: You'll have to find it yourself unless someone else can be more specific.

Jon

macOS 11.7.10, iMac Retina 5K 27-inch, late 2014, 3.5 GHz Intel Core i5, 1 TB fusion drive, 16 GB RAM, Epson SureColor P600, Photoshop CC, Lightroom CC, MS Office 365